As the quality of ore bodies slowly declines and environmental regulations continue to increase, copper producers face challenges with remaining profitable. For example, many producers of copper concentrate rely on a smelter contract, in order to get paid for copper concentrates they produce. Further adding to the challenges and complexities with the business models of copper producers, is that the term of a smelter contract may typically only extend for one year; and therefore, it may not be uncommon for a smelter contract to be re-negotiated annually. Such frequent changes of contract terms regarding minimum acceptable grade of received concentrate and/or maximum acceptable impurity concentration levels leaves copper concentrate producers with continued questions and uncertainties regarding to expected revenue and profitability forecasts.
Smelter contract penalties generally apply to concentrates having a low grade (e.g., low % copper concentration) and/or to concentrates comprising too much of one or more deleterious elements that might be considered to be toxic, considered to be expensive to dispose of, considered to be contaminants to the principal metal to be recovered, considered to present risks to the occupational health of smelter workers, considered to increase environmental disposal costs, considered to reduce copper quality, and/or which may be considered to be difficult to separate or remove. For example, elements including, but not limited to lead, arsenic, cadmium, mercury, and fluorine, which may be present in concentrations, and/or which exceed specified levels defined within the terms of a smelter contract, may incur financial penalties for a concentrator operation selling or further processing its produced final copper concentrate. Moreover, if some elements are found to be high enough in concentration within a produced final copper concentrate, the concentrate may not even be saleable.
Current and past methods which have been disclosed or used by copper concentrators focus on pre-sorting run of mine (ROM) material, in order to maximize the copper grade of the ROM material being fed into the concentrator. In this regard, it is conventionally believed that the expensive reagents, power (e.g., for grinding the ROM material), and water used to extract target metals from ROM material to produce a final copper concentrate product could be more efficiently used by treating only the copper rich portion(s) of a mine which produce copper-rich ROM material. While the concept of pre-sorting ROM material might work in principle, commercially-viable/feasible/practical working embodiments of such techniques do not currently exist. In particular, ROM material pre-sorting technologies which might be able to be used to perform the ore sorting at the level of tonnage required, or, to make the practice of such a method profitable, do not currently exist. Moreover, the large size of most ROM material makes thorough compositional analysis difficult at best.
In addition to pre-sorting incoming ROM material, prior art methods, such as the one described in U.S. Pat. No. 1,808,547 (hereinafter, “the '547 patent”) suggest that a concentrator should be operated to simultaneously produce both a high-grade product, and a low-grade product, along with a tailings fraction; wherein a general concentrate is divided into a high-grade concentrate and a low-grade concentrate for simultaneous parallel treatment (page 6, lines 74-75). Accordingly, such a downstream circuit handling low grade concentrate production would necessarily need to be much larger than a downstream circuit used to produce a small amount of very high grade concentrate. In addition, the '547 patent suggests minimizing the amount of material that is to be smelted (page 6, lines 40-41). Accordingly, prior methods essentially teach away from economical smelting operations which only move a general concentrate to a downstream hydromet circuit on low grade production days. Moreover, prior art methods fail to teach or suggest the concept of intermittently diverting a general concentrate between two downstream processes—for example, as a function of the contents of the general concentrate (e.g., grade or impurity content).
Additional prior art methods have been developed in an attempt to increase profits to copper concentrators. For example, Galvanox™ technology (as discussed in “Galvanox™—An Opportunity for Existing Copper Flotation Concentrators to Improve Overall Project Economics”, Linus Sylwestrzak, Ken Baxter, John Turney, and David Dixon, in Hydrocopper 2009, Antofagasta, Chile, pp. 17-25) suggests means for increasing profits to the concentrator comprising altering the upstream flotation circuit within a concentrator, in an effort to maximize the copper grade of produced concentrates which are destined to be sent to a smelter. It is taught that a copper concentrator might increase its overall copper recovery by leaching cleaner tails—which, according to the aforementioned publication, could be more enriched in copper as a result of the altered upstream flotation circuit within the concentrator. In this latter approach, as with the '547 patent, the major component of the profit is derived from hydrometallurgical processing, and not from smelting. Furthermore, these prior art teachings seem to suggest that existing concentrator operations, particularly the upstream flotation circuit and/or portions thereof within the concentrator, would necessarily have to be substantially altered in order to practice the methods and enjoy the benefits of the methods. Accordingly, with prior methods, a concentrator operation may have to modify is infrastructure (i.e., the upstream equipment, flowsheets, and process conditions which are necessary to produce a final copper concentrate product) in order to allow the concentrator to produce two distinct, and separate product streams simultaneously, in parallel.
In concentrators where the concentrator feed (i.e., crushed ROM material) comes from deposits with large mineralogical variability, the copper grade of the produced final concentrate product can be highly variable and fluctuate regularly. Accordingly, efforts to maintain a target final product grade (i.e., according to a minimum acceptable grade value outlined in a smelter contract) can be costly. It may not be uncommon or impossible for final produced concentrate product having copper concentrations as low as 10% (i.e., poor grade concentrate) to make its way to a smelter on certain production days during the operation of a concentrator. Moreover, final produced concentrate product having as much as 35% copper could make its way to a smelter on better production days. The number of penalties associated with a few bad concentrate production days (e.g., due to ROM material composition fluctuations) may ultimately compromise bottom dollar economics and/or profitability of a concentrator that sells its copper-containing concentrate product to a smelter.
There exists a long-felt need to provide a simple process solution which would allow a concentrator operation to continue to enjoy the continued economic benefits of smelting, without incurring excessive penalties associated with low grade concentrate production days and/or days where smelter feeds exceed maximum allowable impurity threshold(s), without necessarily modifying upstream concentrator operations (e.g., flotation circuit components and/or chemistry), all while still minimizing capital expenditures (CAPEX) and investments which are typically involved in converting an existing smelting operation entirely over to a hydrometallurgical process.